1. Field of the Invention
The present invention relates to the field of manufacturing facility control such as used in a semiconductor manufacturing facility; more specifically, the present invention relates to a method, system, and computer program product for controlling the flow of material in a manufacturing facility using an extended zone of control.
2. Related Art
One of the critical questions that must be answered in a manufacturing facility (e.g., a semiconductor manufacturing facility) is: “what lot to run next on a tool when the tool becomes free?” This is referred to as a “What Next” dispatch decision and is currently determined by what is referred to generically as a What-Next-Module (WNM). This decision is one of a hierarchical set of matching (assets with demand) decisions in which an asset (e.g., a manufacturing tool) can execute one of several manufacturing processes, and a demand is a lot (e.g., a wafer lot) requiring one of the manufacturing processes the tool can execute. The WNM must ensure that various system constraints are not violated (e.g., capacity constraints, lot-to-tool compatibility, batch size limits, etc.). Other constraints can be established by business guidelines (e.g., lot type to tool dedication strategies, tool specific inhibits, phase in tools, etc.). Within these constraints, the WNM attempts to account for a series of dispatching metrics including: priorities, due dates, lot dependent setups, maximizing batch size, work in process (WIP) balancing, and synchronization across the manufacturing facility.
Dispatching ideally identifies the next lot to run on a tool which optimizes the position of the total supply chain based on constraints and metrics such as those described above. Current dispatching-based systems typically rely on real-time list based scheduling in which lots immediately available for dispatch are sorted based on identified criteria, and lots are released based on this priority ordering. These are commonly referred to as “opportunistic dispatching systems.” There is substantial prior art addressing this list-based dispatching. One known method is based on the concept of critical ratio, which is defined as follows:critical ratio=(lot due date−current date)/(standard days processing).
Current dispatching methodologies focus on lots currently waiting to be, or very soon to be, processed at a tool (i.e., in a local zone of control). To this extent, there is little awareness of upstream activities, downstream requirements, and future dispatching decisions (i.e., in an extended zone of control). Such information, if properly utilized, could be used to enhance the performance of the tools within a manufacturing facility and, as a result, overall manufacturing performance.